This invention relates to a constructing method for underground continuous walls of double rows and the structure of double-row continuous walls, particularly to one of a compound constructing method for mass production of continuous double-row wall s having an outer wall and an inner wall, with the intermediate portion between the outer and the inner wall being filled with concrete at work site. A first step of the constructing method is to build a guide wall in the preset range of a location. A second step is to dig a ditch down in the ground based on the guide walls. A third step is to check the verticality of the ditch when the ditch is dug to a preset depth. A fourth step is to wash stop plates, and remove dirt and mud on the bottom of the ditch. A fifth step is to construct a single double-row wall unit for continuous double-row walls at a process site. A sixth step is to place a plurality of the single double-row wall units orderly in the ditch, and pour in concrete from the uppermost wall unit, finishing a round of construction of the underground continuous walls. In this method, each wall unit in the continuous walls is connected to each other stably, effectively preventing water from seeping in, also preventing soil slip and soil mixing in concrete from happening. In addition, it can improve protective layers of reinforcement, insufficient bend stress, rupture of wall bodies, corrosion of steel bars (reinforcement), and improper mixing of sand with concrete. At the same time, an upper and a lower wall unit are screwed together with bolts and nuts to form a unit of continuous walls, with the depth of construction not limited and with management of construction being easy to control.
A conventional method of constructing underground continuous walls generally digs deep ditches around the range of the building location, placing steel bar cages in the ditches (or placing pre-formed PC (precast concrete) plate). Then concrete (or a hardener is poured into two sides of the PC plates to form a wall) is poured into the ditches to form a wall unit of a continuous wall.
However, the conventional method has the following disadvantages.
1. Every two neighboring wall units of a continuous walls are not connected with a secure connecting means, with a gap possibly formed between them, thereby rendering it impossible to tightly connect the units to each other, and thus not satisfying necessary water-tightness and strength requirements.
2. The gap formed between every two neighboring wall units may function as an inlet for water to flow therethrough. Then continuous walls may have water leak, leading to danger to construction and trouble of water leak after completion of the construction.
3. A pouring hole is preset in steel bar cages for pouring concrete to form a single wall unit after concrete hardens. But as ditches are generally narrow and very deep (normally 10 meters or so), and concrete is poured in the ditches full of stabilizing liquid (grouting), causing the steel bar cages to be soiled by the stabilizing liquid to affect its bend stress, also causing soil and mud liable to mix in the concrete to reduce strength of the concrete, and thus lowering strength and quality of the walls.
4. PC (precast concrete) plates are not connected to each other with connecting means, only kept together by hardener filled in the two sides of the PC plate. And mixing propoetion of the hardener and time error can cause property change to the hardener, largely affecting the strength of the whole wall.
5. Its constructing work is effected by pouring concrete into steel bar cages put in dug ditches. But there may be problems in managing construction, verticality of ditches, smoothness of concrete surfaces, insufficient thickness of reinforcement layers. Above all, chances are that rupture of wall bodies, corrosion of steel bars, harming the ground wall, and increasing constructing work may occur.
6. Constructing is done in ditches full of stabilizing liquid, and steel bar cages (or PC plates) are of a large dimensions, causing difficulty in performing construction and in controlling quality. So it is often necessary to construct other walls inside the continuous walls to hide rough or cracked surfaces, reducing the dimensions of a basement, needing frequent reinforcing work, wasting labor and time and materials.